Milo g



(No Model.)

M. G. KELLOGG. MULTIPLE SWITGHBOARD.

Patented Oct. 26, 1897.

a U I..

UNrrnD STATES yPr-iTENT OFFICE.

MILO G. KELLOGG, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE KELLOGGSVITCIIBOARD AND SUPPLY COMPANY, OF SAME PLACE.

MULTIPLE SWITCHBOARD.

SPECIFICATION forming part of Letters Patent No. 592,307', dated October26, 1897.

Application filed Malh 5:1338- To au whom it may concern:

Be it known that I, MILO G. KELLOGG, of Chicago, Illinois, have inventedcertain new and useful Improvements in Multiple Switchboards forTelephone-Exchanges, of which the following is a full, clear, concise,and exact description, reference being had to the accompanying drawings,forming a part of this specification.

My invention relates to a metallic-circuit telephone; and it consists ofapparatus for a system of testing at any board of a multiple exchangesystem to determine whether a line is in use.

In the accompanying drawings, illustrating my invention, Figure l is adiagram illustrating the main-line central-office apparatus and circuitconnections. Fig. 2 shows a diagram of the subscribersstation apparatus.Fig. 3 shows a diagram of an operators cord system for calling andanswering, switching, and clearing out subscribers lines. Fig. 4 showsan operators test system, including a test-plug with cord,test receivinginstrument, and connections.

In Fig. l, A is a sectional view of one switchboard, and A is asectional view of another switchboard, to which the same lines areconnected. I place as many boards in the central office as are foundnecessary or desirable in order to properly answer the calls and inakethe necessary connections. On each board is a spring-jack or othersuitable switch for each line. Each spring-jack has a cont-act-sprin gwhich normally bears on an insulated contact-point and has acontactpiece insulated from the rest of the switch (except by the lineconnection) and is adapted to receive a loopswitch plug and, when theplug is inserted, to disconnect the spring from the contact-point (onwhich it normally bears) and connect the two contact-pieces of i theplug` with the spring and said insulated Serial No. 266,315. (No model.)

through the fronts of which are the holes Z l. These holes are adaptedto receive the switchplugs shown in Fig. 3 and marked D D, and when theplugs are inserted in the switches they operate them as above described.

The insulated contactpieces jj should be so placed that a test-plug orother switch testing device may be readily applied to them.

B is a test-battery, andw is a calling-coinmunicator.

Each subscribers main-line circuit begins, say, at the central officeand passes by a wire, which we will call wire a, to the subscribersstation, through his station apparatus and back to the central office byanother wire, which we will call wire b. One of these wires-say wirea-is connected to all the insulated contact-pieces jj of its switches onthe different boards. The other wire passes successively through thepairs of contactpoints formed by the spring-levers and theircontact-points of its switches on the different boards, passing in eachcase to the springlever first, as shown. This wire after passing fromthe last contact-point of the switch farthest distant from thesubscribers station is connected by a circuit-wire to wire a of thesubscribers circuit. In this circuit-wire thus connecting the two wires,sides, or branches of a metallic-circuit line I place a test-battery.Fig. l shows the connections of one line, as described above. All theother lines of the exchange would be connected through their switchesand test-battery in the saine way. One battery may be used for eachline. It should be strong enough to operate the test receivinginstruments used through the test circuits hereinafter described, but itshould not be strong enough to operate a calling-annunciator or signalbell which may be in the circuit.

In the subscribers-station apparatus shown in Fig. 2 l is thetelephone-switch, 2 is the callinggenerator, 3 is the signal-receivingbell, and 4t is the subscribers telephone. G represents a groundconnection. The circuits of the apparatus are substantially as shown.Where the telephone is on the switch, it closes the pair ofcontact-points shown, one of which is connected with the ground, andthereby grounds the line. When the telephoneis olf TOO from the switch,this ground connection is removed. When the telephone ison the switch,it is short-circuited from the circuit of the line and thesignal-receiving bell 3 is in the direct circuit of the line, while theshort circuit ot' the telephone is automatically removed rby the act oftaking the telephone:` from the switch for use, thus bringing 'it intoIthe direct and unshunted circuit of the line,

so as to receive any signals due to variationsy of current, whethertelephone or otherwise, which may occur in the line-circuit.

Fig. 3 shows an operators cord system fork answering and connectingsubscribers lines, f dac., with one set of loop-switch plugs, dou-f bleflexible cords, looping-in switch, and clearing-out annunciator, and hertelephone and calling-generator and circuits.

holes.

lations. yThe two .contact-pieces of each tplug are xrespectivelyconnected wit'h'the twocon-l tact-pieces of the other by lflexiblecond-.uct-` ors, one `ot' which includes a loop-switch Y, having twolevers that work on pairs of contacts a", so, y y, e z,

the operators telephone between fc' z. The

plugs .D D normally rest upon a met-al plate d, l

with which theircontact-pieces are in contact.

art. Only one calling-generator and one operators telephone are requiredfor all the pairs o'tplugs that may be used wby o'ne oper-- ator.

The operatorstest system shown in Fig.. 4 consists., essentially, ofawire withva test receiving instrument (preferably a vreceivingtelephone)in its circuit, said wire 4being grounded 'at-one'endA and terminatingat its other end with a iexible cordwith a test-plug attached adaptedtobe 'brought into connection with `any of the contact-pieces j j at herboard. In the ligure .F is vthe test-plug, tis the test receivinginstrument, and G is the ground connection. A

Each operator should have a cord, system and a testsystem similar tothose described above, and they should be so placed and mountedthat shecan readily `perform the operations required of her.

In the'operation ot the system the sub.

scriber vwho desires a call operates his -calling-generator, thuscausing his line-annunciator to indicate a call at 'the central office,

and immediatelyaeinoves his telephone from its switch and listenstherein to hear any sigf nal which may come over his line, as is usualin telephone-exchange operation. The operator .at the central office onobserving the indication ofthe line-annunciator placesone r D .D arethe. switch-plugs and 'areadapted to lit theswitchj r m lm are theinsulated contact-pieces of the plugs, and n n are their rubber insu-`The clearing-out ann-unciator is connected between the contact-bolts a:x, the calling-generator between y g/,and

ot her switch-plugs into the switch of the line at her board, thelooping-in switch which belongs to the pair of plugs used being in theposition so that her telephone is in closed circuit with thecord-conductors. The subscriber then tells the operator with what linehe desires connection, and the operator tests the line wanted, as willbe hereinafter indicated, in order to determine whether or not it isswitched for conversation. It she iinds it is not switched forconversation, she places the plug which is the mate to .the one used toconnect with the line of the calling subscriber into the switch of theline wanted, and moves the looping-in switch so that hercalling-generator is looped into the circuit of the two lines, lthusringing the bell of the subscriber wanted. She then moves the looping-in swi'tchso that the clearing-out annunciator is in the circuit ofthelines, and the two lines are thus connected together into a closedcircuit for conversation, with the clearing-out annunciator in thecircuit toreceive any clearingout signal which is sent. When thesubscribers are through conversation, either may operate hiscalling-generator and thereby cause the clearing-out an'nunciator toindicate a signal. The operator thereupon removes the plugs from theswitches of the two lines.

stantly again brought into closed circuit with its line.

dIt willappear from the description of the circuits and apparatus abovemade that an electric current generated by the battery in its circuitwill continually pass through the circuit ofreach line when it is notswitched for conversation. 1t will also appear that when a line isswitched for conversation by a switch-plug being inserted into one ofthe line-switches the complete circuit of the line and the battery willbe automatically and abruptly broken at the contact-points g h of theswitch used, and a new complete circuit ise'stablished for the line ofwhich that part ot the circuit described above in which .is the batteryforms no part. When a line is switched for conversation, nobattery-current, therefore, is passing through its circuit.

It will be understood that each line is grounded at its subscribersstation when it is not in use.

The test-'battery is a source of electricity which provides a current ofsuch character that while on closed circuit with its line it produces nosound in a telephone connected in the ordinary Way in its line-circuitor in a circuit neighboring to its line-circuit. Other sources or.generators of electrical current or currents may be usedwhichaccomplish substantially this result.

It is well knowntha't when a magneto-tele phone is placed in closedcircuit with a battery or when it is'taken from such a closed circuitwith a battery at the instant of vthe IOO IIO

change from the condition when no current is passing through thetelephone to the condition in which current is passing through it, oragain from the condition when current is passing through it to thecondition when no current is passing through it, a click or sound ismade in the telephone which is audible to any one who is listening atit. It follows, therefore, that when a subscriber on operating hisgenerator to operate his line-annunciator at the central office andimmediately takes his magneto-telephone from its switch, as is usuallythe operation, thereby bringing the same into closed circuit with hisline and with the battery which is in circuit with the line at thecentral office, he will hear a click or sound in his telephone when theoperator at the central office places her switch-plug into the switch ofthe subscribers line and thereby disconnects the battery from theline-circuit and at the same time connects her telephone into thecircuit. The subscriber has therefore in this system an automaticindication or signal when the operator has switched or connected hertelephone to his line and can at once speak to the operator and instructher what connection he desires without waiting for the operator to firstspeak and inform the subscriber that she is ready to receive his order.This automatic signal to the subscriber thus given expedites the usualoperation of telephone-exchange systems. It is also well known that inthe old method of operation the subscriber is sometimes uncertainwhether it is the voice of the operator who has connected her telephoneinto the line-circuit and is talking with him or whether it is someextraneous voice due to cross talk or induction which he may hear Whilelistening for the operator to respond to his call and therefore isuncertain whether to answer and hesitates about doing so. lVith theautomatic indication which my system gives to the subscriber thisuncertainty and hesitation will not exist and the subscriber will withpromptness communicate his wishes to the operator.

It is also well known that a subscriber frequently desires to call upand converse with several other subscribers in quick succession. In theusual practice in these cases the subscriber first obtains theconnection with one subscribers line, and after finishing theconversation with him operates his generator to send the clearing-outsignal and then waits for a certain length of time until his judgment orhis experience leads him to believe that thc operator at the centralofce has probably disconnected his line from its connection and placedit in condition to receive a new call. It is, however, frequently amatter of uncertainty with the subscriber whether when he sends thesecond call it operates the clearingout annunciator, thus repeating theclearingout signal, or operates his line-annunciator, thus indicatingthat he desires to give a new order. He is, moreover, uncertain andtroubled in not knowing just how long he had better wait from the timewhen he sent the clearing-out signal to the time when he shall send thesecond signal which he desires to be for a call. The result is that heeither sends the second call too quick after the clearing-out signal wasgiven, thus causing confusion in the operation of the exchange system,or frequently waits longer than is necessary before sending the secondsignal, thus losing time. In this system, however,` the subscriber byplacing his telephone to his ear hears a click in his telephone themoment the operator withdraws the plug from the switch, thus placing theline in condition to receive a new call and will at once send in the newcall. This click arises from the line-battery being automaticallybrought into closed circuit with the subscribers telephone by theoperation of withdrawing the plug from the switch and is an automaticindication to the subscriber that his line is in condition to make a newcall, which will be indicated at the central ofce. A

When an operator at any board desires to test a line to see whether itis in use, she con nects her test-plug to contact-piece j `at her boardof the line, and thereby connects to the line her test receivinginstrument grounded at its other end. By so doing she establishes abranch of derived circuit for those portions of the line which arebetween the subscribers ground and the test-circuit ground describedabove and the test receiving instruments in that derived circuit.` Ifthe subscribers telephone is not switched for conversation and the lineis not switched for conversation and therefore has an electric currentpassing through it, part of the current from the battery will passthrough the test receiving instrument according to the well-known law ofthe division of current through derived circuits. The instrument willVrespond to the current which passes through it and the operator-willhear the click in her telephone. If, on the other hand, the line whichis tested has the subscribers telephone switched for use by beingremoved from its switch or is switched, no current will pass through thetest receiving instrument and no click or sound will be made in the testreceiving instrument. Hearing nothing on making the test she will knowthat the line is in use. 'When she hears the click, on testing she willknow that the line is not in use. When the test is made and the testreceiving instrument responds, it indicates in this system both that theline is not switched at the central office and that the subscriberistelephone is on its switch, and when the instrument does not respond itindicates that either the line is switched at the central ofiice or thatthe subscribers telephone is off from the switch.

In multiple-switchboard systems an operator to whom certain lines areassigned to answer frequently receives several annunciator-calls atpractically the same moment,

IOO

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and it may require some time before she can sw-itch to a certain lineand answer the call. In systems in which the test depends only on theswitching of .the line at some other board another operator may in `themeantime test the line and finding it to vtest free may switch it withanother li-ne and cause annoyance and-confusion to the subscriber. In mysystem this trouble is obViated, because asV soon as the subscriber`takes the telephone from its vswitch the Aline will test busy, whetheror not it isswitched at the central oice'.

Again, in systems of testing which depend only on the subscriberstelephone being on or off its `switch confusion frequently occurs fromthe fact that a subscriber places his telephoneon its switch when he isthrough conversation without sending a clearing-out signal, and his linetests free and is connected to when it is already switched at thecentral ofce with another line. `In my system this trouble again isobviated because the line will test busy until it is disconnected at thecentral office, whether or not the subscribers telephone is on itsswitch. The system therefore combines the advantages and obviates thedisadvantages of both the general systemsof testing outlined above.

The battery in thecircuit of a line, as described above, should be soadjusted to the apparatus and circuits that it will not operate anysignal bells or annunciators which may be in circuit with it. It should,however, be strong enough to operate the test receiving instruments usedthrough the testcircuits described. f

The individual batteries, one for each line, normally in the circuit ofthe lines being a source of constant rather than of pulsatory orintermittent Acurrent furnish the test indications and the signals whichhave heretofore been indicated and at the same time do not furnishsudden variations of current which lmay cause inductive disturbances inneighboring circuits.

Instead of batteries used as above any constantly-operative sources ofelectricity may be employed which, when connected and operated in thecircuit as described, will give a signal indication to the subscriberand a test indication to the operator.

I claim as my inventionl. In a telephone-exchange system,metallic-circuit lines, each line normally or while it is not switchedfor conversation atthe central office on closed circuit there, andbatteries, one for each line at the central office, normally in theline-circuit, in combination with switching apparatus at the centraloffice to switch any line for conversation and by the act of switchingand as long as lthe line is thus switched removing the battery from itscircuit, and a telephone at each subscribers station at the will of thesubscriber in closed circuit with his line, whereby the subscriber maydetermine when the line is switched for use, substantially as set forth.

2. In a telephone-exchange system, metallic-circuit lines, each linenormally or while it is not switched for conversation at the centraloffice on closed circuit there, and sources of electricity, one for eachline at the central office, normally in the line-circuit, in combinationwithv switching apparatus at the central office to switch any line forconversation andV by the act of switching and as long as the line isthus switched removing the source of electricity from its circuit, and atelephone at each subscribers station at the will of the subscriber inclosed circuit with his line, whereby the ysubscriber may determine whenthe line is switched for use, substantially as set forth.

3. In a telephone-exchange system,- telephone-lines, each line normallyor while it is not switched for conversation at the central office onclosed circuit there, and batteries, one for each line at the centraloffice, normally in the line-circuit, in combination with switchingapparatus at the central office to switch any line for conversation andbythe act of switching, and as long as the line is thus switchedremoving the battery from its circuit, and a telephone at eachsubscribers station at the will of the subscriber in closed circuit withhis line, whereby the subscriber may determine when the line is switchedfor use, substantially as set forth. y

4. In a telephone-exchange system, telephone-lines, each line normallyor while it is not switched for conversation, at the central oflice onclosed circuit there, and sources of electricity, one for each line atthe central office, normally in the line-circuit, in combination withswitching apparatus at the central ofiice to switch any line forconversation and by the act of switching andas long as the line is thusswitched, removing the source of electricity from its circuit, and atelephone at each subscribers station at the will of the subscriber inclosed circuit with his line whereby the subscriber may determine whenthe line is switched for use, substantially as set forth. y

5. In a multiple telephone-exchange system, metallic-circuit lines, eachline normally grounded at the subscriber-s station and on closed circuitat the central office, and batteries one for each line at the centraloffice, each normally or while the line is not switched for conversationat the central office in the circuit of its line there but switched fromits said circuit by the act of switching and as long as the line isswitched for conversation there, in combination withatelephone at eachsuhscribers station, a switch with contacts and circuit connectionsswitching the telephone at the will of the subscriber -into the circuitof his line,and opening the normal ground connection of the line at thesubscribers station while the telephone is switched IOO IIO

into its line-circuit, and a test receiving instrument at the centraloffice grounded on one side and connected on its other side to a plugadapted to be brought into connection with any line whereby the operatormay determine Whether, and the subscriber may determine when, the lineis switched for use, substantially as set forth.

6. In a multiple telephone-exchange system, metallic-circuit lines, eachline norm ally grounded at the subscribers station and on closed circuitat the central oiiice, and sources of electricity, one for each line atthe central oce, each normally or while the line is not switched forconversation at the central office in the circuit of its line there butswitched from said circuit by the act of switching and as long as theline is switched for conversation there, in combination with a telephoneat each subscribers station, a switch with contacts and circuitconnections switching the telephone at the will of the subscriber intothe circuit of his line, and opening the normal ground connection of theline at the subscribers station while the telephone is switched into itslinecircuit, and a test receiving instrument Aat the central officegrounded on one side and connected on its other side to a plug adaptedto be brought into connection with any line, whereby the operator maydetermine whether, and the subscriber may determine when, the line isswitched for use, substantially as set forth.

7. In a multiple telephone-exchange system, telephone-lines, each linenormally grounded at the subscribers station and on closed circuit atthe central office, and batteries, one for each line at the centraloffice, each normally or while the line is not switched for conversationat the central office in the circuit of its line there but switched fromits said circuit by the act of switching and as long as the line isswitched for conversation there, in combination with a telephone at eachsubscribers station, a switch with contacts phone at the will of thesubscriber into the circuit of his line, and opening the normal groundconnection of the line at the subscribers station while the telephone isswitched into its line-circuit, and a test receiving instrument at thecentral ofce grounded on one side and connected on its other side to aplug adapted to be brought into connection with any line, whereby theoperator may determine whether, and the subscriber may determine when7the line is switched for use, substantially as set forth.

8. In a multiple telephone-exchange system, telephone-lines, each linenormally grounded at the subscribers station and on closed circuit atthe central office, and sources of electricity, one for each line at thecentral office, each normally or while the line is not switched forconversation at the central oflice in the circuit of its line there butswitched from its said circuit by the act of switching and as long asthe line is switched for conver sation there, in combination with atelephone at each subscribers station, a switch with contacts andcircuit connections switching the telephone at the will of thesubscriber into the circuit of his line, and opening the normal groundconnection of the line at the subscribers station while the telephone isswitched into its linecircuit,and a test receiving instrument at thecentral ofice grounded on one side and connected on its other side to aplug adapted to be brought into connection with any line, whereby theoperator may determine-whether, and the subscriber may determine when,the line is switched for use, substantially as set forth.

MIL() G. KELLOGG.

Witnesses:

J. J. FOSTER, A. A. MALoNn.

